1. Field of the Invention
This invention relates to a multi-function electronic digital watch of the dynamic logic type wherein timekeeping, displaying etc. are performed by sequentially reading out a series of control instructions written in a read only memory (ROM), in accordance with predetermined timing pulses.
2. Description of the Prior Art
In recent years it has now become popular for electronic digital watch to have not only a time indicating function, but also a stop watch function, a timer function, a calender function etc. In cases of intending to realize such multiple functions with static logic, independent logic circuits need to be disposed for the respective functions. This has led to the problems in that a scale of a circuit arrangement as the whole becomes large and that the fabrication of the circuit arrangement in the form of a monolithic IC is difficult. In order to solve this problem, there has been adopted the so-called dynamic logic system wherein a series of control instructions written in a ROM are sequentially read out according to predetermined timing pulses (for example, clock pulses on the order of 4 KHz) defining machine cycles, and predetermined information processings are completed according to the control instructions and within a fixed time interval (for example, 1/10 sec) to provide the time base of the watch, whereby timekeeping, displaying etc. are executed.
With such systems, however, in adding the stop watch function which can measure down to, for example, the digit for 1/100 sec, the time base of the watch needs to be made 1/100 sec. Therefore, the predetermined information processings performed when the time base has been 1/10 sec and also information processings increased by the addition of the stop watch function must be completed within 1/100 sec. In order to cope with this situation, the frequency of the timing pulses needs to be made high. The high frequency is attended with increases in the charging and discharging currents of capacitance elements, stray capacitances etc. of the circuitry, and results in various problems such as an increase in the power dissipation and a lowering in the speed margin in a low-voltage operation.
Besides, since the frequency of an oscillator circuit for a watch is a comparatively low frequency of, for example, 32,768 Hz, it is subject to limitations in making the frequency of the timing pulses high as described above. In order to complete all of the necessary processings within 1/100 sec as stated above, a high frequency oscillator circuit is required. This means that the whole circuit arrangement becomes a high frequency circuit, resulting in problems such as complication of the circuit arrangement and increase in the power dissipation of the oscillator circuit.